During such work as house decoration, maintenance and installation of equipment and materials, the angular value states (e.g., horizontal and vertical) of objects are usually measured and corrected. Existing level bars are mainly read by unaided eyes. It takes time to analyze in work with higher precision, and large precision errors exist, bringing inconvenience to the work, mainly because the control design of the level bar is imperfect. Since observing whether the level bubble is in the middle position of two scale lines with eyes easily results in visual errors, and it is difficult to accurately observe the position of the level bubble in environment with poor light, it is difficult to accurately judge whether an object reaches the set planar state, and thus it is uncertain whether the checked and corrected object can reach the required planar state.